0-4400 RPM: Low-lift cam lobe and long intake runners.
4400-5800 RPM: High-lift cam lobe and long intake runners.
Stage 3 5800+ RPM: High-lift cam lobe and short intake runners.

Listen real close and you will hear a change in the engine a 4400 RPM, but its not as dramatic as when the secondary butterflies open. Used to give the GSR a flatter torque curve. This is part of the reason why the GSR makes almost as much torque as the type r but at 1300 rpm sooner.